Question

I was searching for an answer for this but I didn’t find it. Does anyone have a solution for this kind of problem. I have a set of text variables that I have to write into the .CSV file using Java. I am currently doing a project with JavaScript that calls for Java. This is a function that I have right now that does the job well and writes the text into .CSV line by line.

function writeFile(filename, data)
{
   try
   { 

      //write the data

      out = new java.io.BufferedWriter(new java.io.FileWriter(filename, true));
      out.newLine();
      out.write(data);
      out.close();
      out=null;
   }
   catch(e)   //catch and report any errors
   {
      alert(""+e);
   }
}

But now I have to write parts of text one by one like the example bellow.

first0,second0,third0
first1,second1,third1
first2,second2,third2
.
.
.
first9,second9,third9

So the algorithm goes like this. The function writes first0 with comma then goes to the next line writes first1, goes to next line writes first2 and so one until first9. After that part is done the script goes to the beginning of the file and writes second0 behind the comma, goes to the next line and writes second1 behind the comma and so on. You get the idea.

So now I need java

Answer 1

You might want to consider using Super CSV to write the CSV file. As well as taking care of escaping embedded double-quotes and commas, it offers a range of writing implementations that write from arrays/Lists, Maps or even POJOs, which means you can easily try out your ideas.

If you wanted to keep it really simple, you can assemble your CSV file in a two-dimensional array. This allows to to assemble it column-first, and then write the whole thing to CSV when it’s ready.

package example;

import java.io.FileWriter;
import java.io.IOException;

import org.supercsv.io.CsvListWriter;
import org.supercsv.io.ICsvListWriter;
import org.supercsv.prefs.CsvPreference;

public class ColumnFirst {

    public static void main(String[] args) {

        // you can assemble this 2D array however you want
        final String[][] csvMatrix = new String[3][3];
        csvMatrix[0][0] = "first0";
        csvMatrix[0][1] = "second0";
        csvMatrix[0][2] = "third0";
        csvMatrix[1][0] = "first1";
        csvMatrix[1][1] = "second1";
        csvMatrix[1][2] = "third1";
        csvMatrix[2][0] = "first2";
        csvMatrix[2][1] = "second2";
        csvMatrix[2][2] = "third2";

        writeCsv(csvMatrix);

    }

    private static void writeCsv(String[][] csvMatrix) {

        ICsvListWriter csvWriter = null;
        try {
            csvWriter = new CsvListWriter(new FileWriter("out.csv"), 
                CsvPreference.STANDARD_PREFERENCE);

            for (int i = 0; i < csvMatrix.length; i++) {
                csvWriter.write(csvMatrix[i]);
            }

        } catch (IOException e) {
            e.printStackTrace(); // TODO handle exception properly
        } finally {
            try {
                csvWriter.close();
            } catch (IOException e) {
            }
        }

    }

}

Output:

first0,second0,third0
first1,second1,third1
first2,second2,third2